According to a magnet embedded type permanent magnet motor that has permanent magnets embedded in a rotor core (an interior permanent magnet motor (hereinafter referred to as an “IPM motor” as necessary)), a current phase is controlled biaxially by a d-axis current and a q-axis current. As a result of this, a magnetic field of the permanent magnets is weakened, reluctance torque is effectively used, and high output operation can be made over a wide range.
Further, it is possible particularly for the IPM motor in which the magnets are disposed in a V-shape to effectively use both of torque of the permanent magnets (magnet torque) and the reluctance torque. As a result of this, the output can be improved further.
When a demagnetization field is applied to the permanent magnets by passing the d-axis current, the magnetic field of the permanent magnets is weakened. However, when the demagnetization field is increased, irreversible demagnetization of the permanent magnets may be caused. Particularly, according to the IPM motor in which the magnets are disposed in the V-shape, it is likely that the demagnetization field is concentrated in the vicinity of the d-axis and the irreversible demagnetization is caused.
Meanwhile, according to JP2003-143788A, gaps are formed at end faces on a d-axis side of the magnets. As a result of this, magnetic resistance at an area in the vicinity of the d-axis is increased, the demagnetization field that is caused locally in the vicinity of the d-axis is prevented from passing through the permanent magnets, and the irreversible demagnetization is avoided.